to certain Colours. 1S9 
yue. The use of the tapetum and of the pigmentum nigrum, 
can scarcely be said to be known. We can only infer, that the 
tapetum, if white, might reflect all the rays and absorb none, 
and if black, as in man, it should absorb all the rays and reflect 
none. “ II est difficile,” says Cuvier, “ de soupconner Fusage 
d’une tache si eclatante dans un lieu si peu visible, Monro et 
d’ autres avant lui, ont cru que le tapis du boeuf est vert, 
pour lui representer plus vivement la couleur de son ali- 
ment naturel ; mais. cette explication ne convient pas aux au- 
tres especes.” Cuvier, .Legons (TJnat Comp. tom. ii. 402, 
Birds and fishes may perceive colours as well as animals, though 
they have no tapetum. The vision of man is regarded the most 
perfect, and defective vision in old people, is sometimes produ- 
ced by a deficiency of the black paint. These considerations do 
not, however, lead us to suppose, that the faculty of distinguish- 
ing the harmony of colours depends on the eye, any more than 
the concord of sounds does on the ear. The eye and the ear 
can be regarded only as instruments for bringing the sensoriuni 
or thinking principle of man and animals acquainted with what- 
ever is visible or audible. The faculty, therefore, must reside 
elsewhere. Quickness of vision never made a Newton, nor deli- 
cacy of hearing a Handel, nor fineness of touch a lieynolds, 
nor acuteness of smelling a Davy, nor accuracy of taste any phi-, 
losopher whatever. For all that man sees, hears, touches, 
smells, and tastes, constitutes only a specific diflerence in his sen- 
sations. These several sensations are compared, judged of, and 
distinguished from each other, by some internal principle which 
does not reside in the organs themselves. It is this principle or 
discriminating faculty of colours which is wanting in Mr 11. Tucker. 
Pressure made on the optic or auditory nerves entering the 
brain, will paralyse these organs which can neither see nor hear, 
unless their communication with the brain be preserved. Am- 
aurosis sometimes arises from disease in the brain, and deafness 
from a similar cause. The brain is the sensitive centre -which 
feels all the sensations of light, sound, odour, and taste. In 
palsy, the latter is often annulled. In the instance of Mr B. 
Tucker, there is no evidence whatever, to lead a person to sup- 
pose, that defect exists in the functional office of his eyes, for his 
vision is quick above par. Where, therefore, does the fault lie ? 
His eyes do their office, but the subsequent processes of perceiv- 
